I just installed some corvette halfshafts with new u-bolts/u-strap and they had these kinda deep gouges on the shank between the u & threads. I assume they were from pressing the U. Anyways now I'm starting to think maybe I should buy others after looking at some u-strap pics online and not seeing the marks. I got them form a corvette places and they also used 15mm nuts instead of 9/16, weird.

I know as much as I can learn and try to keep an open mind to anything!

Either the edge of the die was worn, or sharp even, or no lube was used when pressed. Or there was insufficient clearance between punch and die to form without dragging.

If it bothers either replace or if the galling is not that deep, linish the marks out. I'd send them back, if only to make the seller aware there's an issue or make good, and depending order elsewhere.

The 'metric' nut sizing seems to suggest they're using common metric nut cold forged blanks for availability/cost, but using an imperial tap for 'correct' thread. Hybrid style, it's not uncommon.

"If an honest man is wrong, after demonstrating that he is wrong, he either stops being wrong or he stops being honest." Anon